Im using the 12" open-web engineered joists. My toilet is against an inside wall, and the waste pipe has to run horizontally not vertically. I can put a WYE right under the toilet to run my vent, and then elbow to make my horizontal run. My problem is, I have about 26' to go horizontally till I can make my vertical drop. The engineered joists only have 8" worth of room, take away the 3 1/2" height of the pipe and that only leaves me with 4 1/2" to make a slope. That will take me all of 18'. Factor in the sanitary T and that 18' gets cut down to about nothing. I dont have enough room for my 1/4" per foot slope.

Any options besides hanging the drain pipe below my joists ? Its in my garage, but still hate to have to do it. I bought these engineered joists to avoid this, and they have been nothing but a pain. Weaker than regular lumber, and a tight fit for most mechanicals.